One of the biggest nutrition myths is that certain foods manipulate your metabolism. There is no food that is going to significantly speed up on slow down your metabolism to such an extent that you should actively pursue eating or not eating them.

Don't believe anyone who tells you that lettuce slows down your metabolism, because this is just not true. Lettuce doesn't do anything to your metabolism.

Research has shown that eating lettuce before a meal, like in a salad, can help you eat about 10 percent fewer calories at that meal. This makes lettuce are great fat-loss diet food, so eat all you want.

Another popular belief floating around is that drinking green tea will help speed up your metabolism. Green tea has a modest thermogenic effect, meaning that it can increase the amount of calories that your body burns via heat.

However, these effects are so minor in the context of your diet and life that having two tablespoons of ranch dressing instead of one on your next salad will completely negate its metabolism-boosting effects.

If you're looking for a foolproof way to speed up your metabolism, focus instead on lifting weights to build more muscle. An intense workout will rev up your metabolism and allow it to stay working at a higher gear for hours afterwards.

Mike Roussell, Ph.D., is the Men's Health nutrition advisor. He holds a degree in biochemistry from Hobart College and a doctorate in nutrition from Pennsylvania State University. His research has been published multiple times in the American Journal of Clinical Nutrition.